When a power supply system is constructed, important challenges are not only to safely expand a power transmission network but also to construct the system so that a large quantity of natural energy can be introduced into the system in the future. Therefore, as a new power network, a power network system called “digital grid” (registered trademark) has been proposed (Patent Literature 1: U.S. Pat. No. 4,783,453, Non-Patent Literature 1: see the web site of The Digital Grid Consortium, http://www.digitalgrid.org/index.php/jp/). The digital grid (registered trademark) is a power network system in which a power network is sub-divided into small cells and these cells are connected with each other in an asynchronous manner. The size of each power cell ranges from a smaller one such as a cell corresponding to one house, one building, or one commercial facility to a larger one such as a cell corresponding to one prefecture or one municipality. Each power cell includes loads and, in some cases, a generator facility and/or a power storage facility. Examples of the generator facility include generator facilities using natural energy such as a solar generator, an aerogenerator, and a geothermal power plant.
Power cells are connected with each other in an asynchronous manner so that electricity can be generated inside a cell without restraint and power is flexibly supplied and received (hereinafter called “interchanged”) between power cells. (That is, although a plurality of power cells are connected to each other, the voltage, the phase, and the frequency of the power used in each power cell are asynchronous to (i.e., different from) each other.)
FIG. 36 shows an example of a power network system 10. In FIG. 36, a core system 11 transmits backbone power from a large-scale power plant 12. Further, a plurality of power cells 21 to 24 are disposed. The power cells 21 to 24 include loads such as houses 31 and buildings 32, generator facilities 33 and 34, and power storage facilities 35. Examples of the generator facilities include a solar generator panel 33 and a wind turbine 34. The power storage facility is, for example, a storage battery 35. In the specification of the present application, generator facilities and power storage facilities are also collectively referred to as “distributed power supplies”.
Further, the power cells 21 to 24 include their respective power routers 41 to 44 each of which serves as a connection inlet/outlet (connection port) for connection to other power cells and/or the core system 11. Each of the power routers 41 to 44 includes a plurality of legs (LEGs). (Because of the width of the paper, the symbols of the legs are omitted in FIG. 36. White circles in the power routers 41 to 44 represent the connection terminals of their legs.)
Note that each leg includes a connection terminal(s) and a power conversion unit(s), and has an address assigned thereto. Note that the power conversion by a leg means a conversion from an AC (Alternating Current) into a DC (Direct Current), a conversion from a DC to an AC, or a change in the voltage, the frequency, or the phase.
All the power routers 41 to 44 are connected to a management server 50 through a communication network 51, and managed and controlled by the management server 50 in a unified manner. For example, the management server 50 provides an instruction for power transmission or power reception performed by each leg to the power routers 41 to 44 by using the address assigned to each leg. In this way, a power interchange between power cells is performed through the power routers 41 to 44.
By enabling a power interchange to be performed between power cells, it is possible, for example, to enable a plurality of power cells to use one common generator facility 33 or 34 and/or one common power storage facility 35. If surplus power is reciprocally interchanged between power cells, it is possible to stably maintain the power supply/demand balance while considerably reducing the facility costs.
Further, Patent Literature 2 discloses a technique related to a power management system for associating the supply source of power with its consumer. In the power management system according to Patent Literature 2: an energy (i.e., electric energy) is measured for each of categories such as an AC apparatus, a solar battery, a fuel cell, a storage battery, and a DC apparatus; power attribute records, which are a group of information pieces corresponding to and associated with the measured power, are generated; and power that is supplied from each power supply system of commercial power supply and power that is output thereto are managed based on the power attribute records. In particular, each power attribute record holds information indicating which generator facility the electricity is generated by.